Subpixel rendering

About: Subpixel rendering is a research topic. Over the lifetime, 3885 publications have been published within this topic receiving 82789 citations.

Methods, systems, and programming for computer display of images, text, and/or digital content

Abstract: A bitmap of a shape, such as a font, can be subpixel optimized by producing for each of a display's subpixels a coverage value representing the percent of its area covered by the shape being represented and by distributing, to prevent color imbalance, an amount of a given subpixel's coverage value to nearby subpixels of different colors as a function of the percent of the given subpixel's coverage value that causes color imbalance. Web pages can be displayed with scaled-down and subpixel optimized images. A given layout of a Web page can be displayed at each of at least two different selected scale factors, with the font bitmaps used to represent characters in the display at each scale factor having their shape and pixel alignment selected to improve readability for the particular pixel size at which they are displayed at each such scale factor.

High-Accuracy Subpixel Image Registration Based on Phase-Only Correlation

Abstract: This paper presents a high-accuracy image registration technique using a Phase-Only Correlation (POC) function. Conventional techniques of phase-based image registration employ heuristic methods in estimating the location of the correlation peak, which corresponds to image displacement. This paper proposes a technique to improve registration performance by fitting the closed-form analytical model of the correlation peak to actual two-dimensional numerical data. This method can also be extended to a spectrum weighting POC technique, where we modify cross-phase spectrum with some weighting functions to enhance registration accuracy. The proposed method makes possible to estimate image displacements with 1/100-pixel accuracy. key words: image registration, subpixel registration, image matching, phase-only correlation, phase correlation

Robust image registration using log-polar transform

Abstract: This paper describes a hierarchical image registration algorithm for affine motion recovery. The algorithm estimates the affine transformation parameters necessary to register any two digital images misaligned due to rotation, scale, shear, and translation. The parameters are computed iteratively in a coarse-to-fine hierarchical framework using a variation of the Levenberg-Marquadt nonlinear least squares optimization method. This approach yields a robust solution that precisely registers images with subpixel accuracy. A log-polar registration module is introduced to accommodate arbitrary rotation angles and a wide range of scale changes. This serves to furnish a good initial estimate for the optimization-based affine registration stage. We demonstrate the hybrid algorithm on pairs of digital images subjected to large affine motion.

GETNET: A General End-to-End 2-D CNN Framework for Hyperspectral Image Change Detection

Abstract: Change detection (CD) is an important application of remote sensing, which provides timely change information about large-scale Earth surface. With the emergence of hyperspectral imagery, CD technology has been greatly promoted, as hyperspectral data with high spectral resolution are capable of detecting finer changes than using the traditional multispectral imagery. Nevertheless, the high dimension of the hyperspectral data makes it difficult to implement traditional CD algorithms. Besides, endmember abundance information at subpixel level is often not fully utilized. In order to better handle high-dimension problem and explore abundance information, this paper presents a general end-to-end 2-D convolutional neural network (CNN) framework for hyperspectral image CD (HSI-CD). The main contributions of this paper are threefold: 1) mixed-affinity matrix that integrates subpixel representation is introduced to mine more cross-channel gradient features and fuse multisource information; 2) 2-D CNN is designed to learn the discriminative features effectively from the multisource data at a higher level and enhance the generalization ability of the proposed CD algorithm; and 3) the new HSI-CD data set is designed for objective comparison of different methods. Experimental results on real hyperspectral data sets demonstrate that the proposed method outperforms most of the state of the arts.

Subpixel measurements using a moment-based edge operator

Abstract: Recent results in precision measurements using computer vision are presented. An edge operator based on two-dimensional spatial moments is given. The operator can be implemented for virtually any size of window and has been shown to locate edges in digitized images to a twentieth of a pixel. This accuracy is unaffected by additive or multiplicative changes to the data values. The precision is achieved by correcting for many of the deterministic errors caused by nonideal edge profiles using a lookup table to correct the original estimates of edge orientation and location. This table is generated using a synthesized edge which is located at various subpixel locations and various orientations. The operator is extended to accommodate nonideal edge profiles and rectangularly sampled pixels. The technique is applied to the measurement of imaged machined metal parts. Theoretical and experimental noise analyses show that the operator has relatively small bias in the presence of noise. >